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Kerry Emanuel on climate change and hurricanes

A satellite measurement of Hurricane Harvey on Aug. 25 found that intense storms in the eastern side were dropping rain at a rate greater than 3.2 inches (82 mm) per hour.Credits: NASA/JAXA, Hal Pierce.

“‘[With global warming, we could see] a 50-percent increase in the destructive potential” of the most powerful tropical storms,’ says meteorologist Kerry Emanuel of the Massachusetts Institute of Technology.”

Now we’re once again deep into storm season around the world, and it’s not pretty. With events still unfolding in Texas with Hurricane/Tropical Storm Harvey, and weeks of escalating devastating monsoon floods in Bangladesh, India and Nepal, many people are asking: are these extreme storms the result of climate change?

The current thinking: it’s complicated. Foremost, we shouldn’t be seeking a direct causal link between climate change and any particular storm. As Professor Emanuel told The Washington Post’s Chris Mooney a few days ago:

“My feeling is, when there’s a hurricane, there’s an occasion to talk about the subject,” he said. “But attributing a particular [weather] event to anything, whether it’s climate change or anything else, is a badly posed question, really.”

Scientists are clear that climate change has “threat multiplier” effects on storms, increasing the likelihood and severity of some aspects. For instance: warmer waters and warmer air increase the moisture available and the energy in storms; disruptions in atmospheric circulation increase the likelihood of a storm “stalling out” over a region; and ocean storm surges are made more destructive when melting ice caps have raised the baseline sea level.

“The thing that keeps forecasters up at night is the prospect that a storm will rapidly gain strength just before it hits land,” Emanuel recently told Agence France-Presse, citing Harvey as an example. “Global warming can accentuate that sudden acceleration in intensity.”

Interestingly, it’s still uncertain whether global warming will lead to more or less frequent hurricanes. But in terms of catastrophic damage, storm frequency seems less important than the severity of storms, where climate change does have a clear footprint.

Kerry Emanuel has been a frequent contributor on OCW. Check out these two courses particularly connected to the storms + climate change issue.

12.103 Science and Policy of Natural Hazards introduces the science of natural catastrophes such as earthquakes and hurricanes and explores the relationships between the science of and policy toward such hazards. It presents the causes and effects of these phenomena, discusses their predictability, and examines how this knowledge influences policy making.

12.340 Global Warming Scienceprovides a scientifically rigorous foundation to understand anthropogenic (human-caused) climate change, an introduction to climate models, the material impacts of climate change, and the science behind mitigation and adaptation proposals. [See also the archived MITx on edX version of this course.]

Want to get into a global conversation about this? Check out the growing community on MIT ClimateX.